Various systems for cleaning floor surfaces are known. At present, the two most common systems on the market are disc systems and cylindrical systems. Disc systems comprise a flat disc being fitted with brushes or pads which is rotated around an axis perpendicular to the surface plane. Having the advantage of a large contact area with the floor and being very flexible concerning the adaptation to different cleaning tasks due to a variety of pad/brush configurations, disc systems have the following drawbacks, though. Firstly, tool pressure and tool diameter are limited: the maximum tool pressure is defined by the machine weight minus the necessary weight for sufficient traction and in some cases also by pressure needs due to the suction system; the diameter is limited by the effect of centrifugal forces. Furthermore, the drive performance of the motor increases with the pressure—this influences motor size, costs and machine autonomy: for many cleaning purposes, a high weight is needed which results in a high power consumption. Finally, disc systems show different agitation directions at different points of the working area as well as changing agitation parameters with increased moving speed of the machine: at higher speed, the moving speed is added on one side of the disc, whereas it is substracted on the other side such that the relative speed can even be zero in some areas.
Cylindrical systems comprise a cylindrical brush which is rotated around an axis parallel to the surface plane. In contrast to disc systems, cylindrical systems have constant agitation parameters over the full cleaning area and a high specific brush pressure due to the cylindrical brush being rotated around an axis parallel to the floor. However, cylindrical systems have other drawbacks. Firstly, the tools are very expensive and have a highly restricted versatility. Secondly, the contact area with the floor is very small: thus, at a higher moving speed of the machine, the agitation time becomes very short. Furthermore, the relative cleaning speed of the bristles can be zero over the whole length of the tool and the overall cleaning result is worse. Finally, cylindrical systems have a high power consumption.
Another system for cleaning surfaces makes use of the principle of a vibrating sander. GB 1 090 365, 2 086 216 and 2 280 843 disclose floor cleaning, scrubbing or polishing devices wherein cleaning means—brushes, pads or the like—is fixed to the underside of a vibrating plate which undergoes a horizontal vibration movement. The plate is attached to an upper stationary frame via flexible connecting members on its upper side, and the horizontal vibration movement is achieved by the rotation of an eccentric vertical drive shaft. Although the cleaning means according to this system have a large contact area with the floor and constant agitation parameters almost over the full cleaning area, they undergo a randomly vibrating movement which does not provide for an efficient transportation of dirt and cleaning solution in a determined direction.
GB 516 405 discloses a machine for grinding or polishing surfaces. As in the last mentioned systems using the vibrating sander principle, an eccentric movement of vertical shafts is utilized to create a horizontal circular movement of working implements. However, instead of being connected to a stationary frame via resilient members and being vibrated around a single eccentric shaft, several working implements are driven in a circular translatory motion each by a plurality of driving crank members. By arranging the cranks opposed in respect of two implements of a pair, but rotating the implements of this pair in the same rotation direction, the implements are moved in such a manner that they cooperate two by two such that each pair will neutralize the forces deriving from the movements. However, since GB 516 405 is concerned with polishing or grinding an already clean surface and not with cleaning it from dirt, it is not disclosed how the dirt is actually removed.